Visual display systems, such as flight simulation systems, are commonly employed to train military, commercial and other personnel. Conventional visual display systems include one or more screens onto which a video image is projected by one or more projectors, such as cathode ray tubes (CRTs). The operator of the visual display system is also generally provided with a control panel and, in some instances, a joystick for providing input to the visual display system in response to the displayed video image. Thus, the operator can simulate the flight of an aircraft, for example, and can respond to the environment as depicted by the visual display.
In conventional flight simulation systems in which a full color video image is displayed, one projector, generally termed an RGB projection, is typically associated with each screen of the visual display system to project the red, green and blue color components of the video image on the associated screen. A typical RGB projector produces video images, each of which consist of a predetermined number of video lines, and each line of which consists of a predetermined number of picture elements, or pixels. For example, a conventional projector produces 1,024 video lines, each consisting of 1,280 pixels. In addition, the video images are produced at a predetermined frequency or frame rate, such as 30 or 60 hertz.
In order to provide a relatively large display for the operator, the video image produced by the projector of a conventional flight simulation system is generally expanded and displayed upon a screen having a much larger surface area than the surface of the projector. For example, each optical line pair of a conventional projector generally defines a projection angle of 12 to 18 arcminutes. Thus, while a relatively large image is displayed for the operator, the resolution of the image is somewhat diminished by the expansion of the video image.
In order to improve the resolution of one portion of the projected video image, systems and methods have been developed to inset a high resolution video image into the displayed video image or background image. The high resolution inset image is generally relatively small and is, for example, positioned at an area of interest. Typically, a portion of the background image is removed or blanked at the area of interest at which the inset image will be displayed. The portion of the video display, from which the background image is blanked, is then replaced with the high resolution inset image. The inset image is generally produced by another projector. The projector which produces the inset image can be an RGB projector to produce a full color inset image, or a monochrome projector which produces a single color inset image.
For example, as disclosed in U.S. Pat. No. 5,242,306 which issued Sep. 7, 1993 to Ralph W. Fisher (hereinafter the "'306 patent"), a video graphic system for producing a wide field color display is disclosed in which an inset area of interest of relatively high resolution is provided in the wide field color display of somewhat lower resolution. According to the video graphic system of the '306 patent, only one color, such as green, for example, is blanked from the background image at the area of interest. A high resolution inset image is then projected to fill the inset area of interest. The inset image is produced by a monochrome projector which produces an inset image in the single color, such as green, which was blanked from the background image. Since only one color is blanked from the background image at the area of interest the remaining two colors of the background image are projected in the area of interest along with the monochromatic inset image. The video graphic system of the '306 patent, however, only provides one high resolution inset image at a single area of interest within the background image.